A third generation partnership project (3GPP) mobile system based on a wideband code division multiple access (WCDMA) radio access technology has been widely deployed all over the world. A high-speed downlink packet access (HSDPA), which is a first step in the evolution of the WCDMA, provides the 3GPP with a radio access technology having high competitiveness. However, since radio access technology has been continuously developed in view of requirements and expectations of users and providers, evolution of a new technology in the 3GPP is required to increase competitiveness. There are required reduced cost per bit, increased service availability, flexible use of a frequency band, a simple structure and an open interface, and adequate power consumption of a user equipment.
In general, a base station serves in a cell. A plurality of user equipments may be located in the cell. There is needed an identifier for distinguishing a user equipment from one another in the cell when the user equipment accesses the base station so as to transmit traffic data. The base station identifies the user equipment using the identifier. Since the number of the identifier is designed in consideration of the maximum number of the user equipments in the cell, the number of, bits to represent the identifier is generally large.
Since it is limited to transmit a large amount of bits during handover or an initial access process, the identifier having large bits may increase signaling overhead.
There is needed a method of reducing the signaling overhead during handover or initial access process.